1. Field of the Invention
The present invention relates to a fuel property sensor that senses a property of fuel at a fuel tank and a fuel tank assembly having the same.
2. Description of Related Art
For example, Japanese Unexamined Utility Model Publication No. S64-53957A teaches a fuel property sensor, which is connected to a middle of a fuel pipe line in a fuel tank of a fuel tank assembly and includes two electrically conductive members exposed in fuel in the fuel pipe line. A controller applies a DC current between the two electrically conductive members and determines an ethanol concentration in the fuel based on the amount of conducted current between the two electrically conductive members.
Furthermore, Japanese Unexamined Utility Model Publication No. H01-148854A teaches another fuel property sensor that includes two cylindrical tubular bodies, which are made of an electrically conductive material and are coaxially placed in a delivery pipe made of a dielectric material while the two cylindrical tubular bodies are electrically insulated from each other. Fuel flows through a gap between the two cylindrical tubular bodies.
In the case of the fuel property sensor recited in Japanese Unexamined Utility Model Publication No. S64-53957A, since the fuel property sensor is placed in the fuel pipe line, two pipe connections are provided at opposed ends of the fuel property sensor. Thus, the number of pipe connections in the middle of the fuel pipe line is increased, and thereby the number of assembling steps is also disadvantageously increased. In the case of the fuel property sensor recited in Japanese Unexamined Utility Model Publication No. H01-148854A, the fuel property sensor is placed in the delivery pipe, so that the number of pipe connections is not increased. However, the delivery pipe is installed to the engine in such a manner that the longitudinal direction of the delivery pipe is parallel to the horizontal direction. Thus, the two cylindrical tubular bodies of the fuel property sensor are placed such that the axial direction of the two cylindrical tubular bodies is placed parallel to the horizontal direction. Thus, foreign contaminants (foreign objects), which are contained in the fuel, tend to be held in the gap between the two cylindrical tubular bodies. Thereby, the fuel property measurement accuracy of the fuel property sensor may possibly be deteriorated.
The present invention addresses the above disadvantages.
According to the present invention, there is provided a fuel property sensor that senses a property of fuel at a fuel tank, which has a tank main body and a flange fixed to the tank main body to close an opening hole of the tank main body. The fuel property sensor includes a housing and first and second electrodes. The housing defines a fuel flow passage and is installed to the flange. The fuel flow passage of the housing communicates between an inside and an outside of the tank main body to conduct the fuel therethrough. The first and second electrodes are made of an electrically conducive material and are exposed in the fuel flow passage in the housing such that the first and second electrodes extend generally parallel to a flow direction of the fuel in the fuel flow passage and are spaced from each other by a predetermined distance. The fuel property sensor determines the property of the fuel based on a capacitance, which is generated between the first electrode and the second electrode.
One end of the fuel flow passage of the housing is placed in the inside of the fuel tank, and the other end of the fuel flow passage is placed at the outside of the fuel tank. A fuel pipe line is connected to the other end of the fuel flow passage. A fuel path of the flange, which is originally present regardless of whether the fuel property sensor is provided or not, is used as the fuel flow passage of the housing (the constituent part of the fuel property sensor). In this way, the fuel property sensor can be provided without increasing the number of pipe connections in the fuel pipe line (fuel pathway).
Normally, the fuel pipe line, which supplies the fuel to the engine, is connected to the other end (the fuel tank outside end) of the fuel flow passage of the housing. In order to protect the connection between the fuel path (the fuel flow passage of the housing) and the fuel pipe line as well as the downstream side portion of the fuel pipe line located on the downstream side of this connection from, for example, stones scattered or bounced from the road surface, the flange is provided on the upper side of the fuel tank, which is placed at the upper side upon installation of the fuel tank to the vehicle. Thus, the flow direction of the fuel in the fuel flow passage of the fuel property sensor generally coincides with the top-to-bottom direction (the vertical direction) of the vehicle. Thereby, the axial direction of the first and second electrodes also generally coincides with the top-to-bottom direction of the vehicle. Therefore, even when the foreign contaminant (foreign object) is introduced between the first electrode and the second electrode, it is possible to limit the long time presence of the foreign contaminant therein by the action of the gravity.
According to the present invention, there is also provided a fuel tank assembly, which includes the fuel tank and the above fuel property sensor.